Extremely high frequency (EHF) is the highest radio frequency band, covering the range of frequencies from 30 to 300 GHz. Compared to wireless applications operating below this band, the free space path loss is much higher. Hence, antenna arrays with beamforming are used to achieve transmission over a longer distance.
Within the EHF band, a 7 GHz band around 60 GHz is envisaged for different emerging wireless communication applications. The number of antenna paths can be different for different applications. For distances up to 10 meter (e.g. transfer of HDTV data between a HDTV and a high-definition DVD player) an array of 16 antennas might be needed. For distances up to a few meters, less antenna paths (e.g. four) might be enough. A number of N antennas corresponds in the receiver to N antenna paths, which need to be combined. It is a challenge to combine so many paths without loss of performance.